Semiconductor devices including compounds such as GaN and AlGaN have many merits such as wide and adjustable band gap energy and thus may be variously used as light emitting devices, light receiving devices, various kinds of diodes, or the like.
In particular, light emitting devices using group III-V or II-VI compound semiconductors or light emitting devices such as a laser diode may implement various colors such as red, green, blue, and ultraviolet due to the development of thin film growth technology and device materials, and may implement efficient white light rays by using fluorescent materials or combining colors. These light emitting devices also have advantages with respect to low power consumption, semi-permanent life span, fast response time, safety, and environmental friendliness compared to conventional light sources such as a fluorescent lamp, an incandescent lamp, or the like.
In addition, when light receiving devices such as optical detectors or solar cells are produced using group III-V or II-VI compound semiconductors, an optical current may be generated by light absorption in various wavelength ranges through development of device materials. Thus, light may be used in various wavelength ranges from gamma rays to radio wavelength regions. Also, the light receiving devices have the advantages of fast response time, stability, environmental friendliness, and ease of adjustment of device materials and may be easily used to power control or microwave circuits or communication modules.
Accordingly, semiconductor devices are being extensively used in the transmission modules of optical communication means, light emitting diode backlights substituted for cold cathode fluorescence lamps (CCFL) forming the backlights of liquid crystal display (LCD) devices, white light emitting diode lamps to be substituted for fluorescent bulbs or incandescent bulbs, car headlights, traffic lights, and sensors for detecting gas or fire. In addition, semiconductor devices may also be extensively used in high-frequency application circuits or other power control devices and even communication modules.
In particular, a light emitting device that emits ultraviolet wavelength light may be used for curing, medical, and sterilization purposes due to its curing or sterilizing action.
However, a light emitting device that emits ultraviolet wavelength light has a high aluminum composition, and thus electric current is not well spread in a semiconductor layer. Accordingly, this causes a decrease in optical output power and an increase in operating voltage.